Field of the Invention
The invention pertains to the use of arrays of color LEDs as a color light-field image sensors.
Description of the Related Art
Light detection is typically performed by photosite CCD (charge-coupled device) elements, phototransistors, CMOS photodetectors, and photodiodes. Photodiodes are often viewed as the simplest and most primitive of these, and typically comprise a PIN (P-type/Intrinstic/N-type) junction rather than the more abrupt PIN (P-type/N-type) junction of conventional signal and rectifying diodes.
However, virtually all diodes exhibit some degree of photovoltaic properties. In particular, LEDs, which are diodes that have been structured and doped for specific types of optimized light emission, can also behave (with at least low-to-moderate performance) as photodiodes. In popular circles, Forrest M. Mims has often been credited as calling attention to the fact that that a conventional LED can be used as a photovoltaic light detector as well as a light emitter, see, for example, Mims III, Forrest M. “Sun Photometer with Light-emitting diodes as spectrally selective detectors” Applied Optics. Vol. 31, No. 33, Nov. 20, 1992, incorporated herein by reference. It was further shown that as photodetectors, LEDs exhibit spectral selectivity associated with the LED's emission wavelength. More generally, LEDs, organic LEDs (“OLEDs”), organic field effect transistors, and other related devices exhibit a range of readily measurable photo-responsive electrical properties, such as photocurrents and related photovoltages and accumulations of charge in the junction capacitive structure of the LED.
What is needed are novel systems and methods for leveraging the aforesaid properties of LEDs for light detection.